The present invention relates to a photometry device applicable to a SLR (Single Lens Reflex) camera, and more particularly to a photometry device with which exposure errors due to a difference of reflectivity of objects having different colors can be compensated.
Recently, in most of cameras, reflection type photometry devices are employed. The reflection type photometry device receives the light, which is reflected by an object and passed through an observing optical system of a camera, using a light receiving element, determines the brightness of the object based on the output of the measured value, and then calculates the exposure value of the camera based on the measured brightness. However, this type of the photometry device cannot detect the color of the object because of its structure. Accordingly, in such a device, the reflectivity of an object is generally assumed to be 18% and the exposure parameter is determined on this assumption. Therefore, regarding a whitish object whose reflectivity is greater than 18%, the brightness is measured as greater than the actual brightness. If the camera controls an exposure operation based on thus determined exposure value, the object is under exposed. A dark object whose reflectivity is less than 18% is measured to have a lower brightness. Therefore, such an object is overexposed. The difference of the reflectivity of the object may also occur depending on the color of the object. For example, when the color of an object is yellow, the reflectivity may be up to 70%. In such a case, if the standard exposure value is for the object whose reflectivity is 18%, the exposure value is approximately 2 Ev lower than necessary. If the object color is blue, the reflectivity is approximately 9%. In this case, the object is over exposed by approximately 1% greater than necessary.
Therefore, in the conventional photometry device, photographer should guess the reflectivity of the object. Then, based on the reflectivity determined by the photographer, the exposure is controlled such that, if the object is a whitish or yellowish one having a relatively high reflectivity, it is to be overexposed, and if the object is a blackish or bluish one having a relatively low reflectivity, it is to be underexposed. With this operation, the above-described defects may be solved. However, to guess the reflectivity of the object and control the exposure can be done by only experienced and skilled photographers. It is impossible to require all the photographers to do such an operation. Further, it is not preferable that a manual operation of the photographer is required for exposure. Further, if such a manual operation is required, cameras become unsuitable for recent trend of the automatic photographing.
It is therefore an object of the invention to provide an improved photometry device with which appropriate exposure values can be obtained regardless of difference of reflectivity of focused objects.
For the above object, according to the invention, there is provided a photometry device for a camera, which is provided with a normal light metering system having spectral sensitivity characteristics close to visual sensitivity characteristics, a plurality of light metering system shaving spectral sensitivity characteristics that are different from those of the normal light metering system, an exposure amount determining system that determines an exposure amount of an object in accordance with an output of the normal light metering system, a colorimetry system that judges a color of the object in accordance with the outputs of the plurality of light metering systems, a compensation amount determining system that determines an exposure compensation amount in accordance with the color judged by the colorimetry system. The colorimetry system divides the photometry area into a plurality of areas and performing colorimetry for each of the plurality of areas, and the compensation amount determining system determines the exposure compensation amounts respectively corresponding to the plurality of areas, one of the plurality of compensation amounts being selected in accordance with at least one of the plurality of areas corresponding to a focused portion of the object, and a controller that compensates for the exposure amount determined by the exposure amount determining system in accordance with the determined exposure compensation amount.
With the above configuration, an appropriate exposure values can be obtained regardless of difference of reflectivity of focused objects.
Optionally, the camera may include a distance measuring system that detects distances of object at a plurality of distance measuring points corresponding to the divided plurality of areas of the photometry area, and a focusing system that focuses on one of the plurality of distance measuring points. In such a camera, the compensation amount determining system selects the exposure compensation amount corresponding to an area in the divided areas of the photometry area including at least on of the plurality of distance measuring point.
Optionally, the plurality of light metering systems are arranged on an eyepiece optical system side of a pentagonal prism of an single lens reflex camera. A photometry area of each of the plurality of light metering system covers a photographing angle of view of the single lens reflex camera. Further, the plurality of distance measuring points are arranged inside the photographing angle of view of the single lens reflex camera.
In the above case, at least one of the divided areas of the photometry area may include one of the plurality of distance measuring points.
Still optionally, the photometry device may be configured such that, the camera is provided with a distance measuring system that detects distances of object at a plurality of distance measuring points respectively corresponding to the divided areas of the photometry area, and a focusing system that focuses on one of the plurality of distance measuring points. The compensation amount determining system may determine an entire exposure compensation amount based on at least one of the weighted exposure compensation amounts corresponding to at least one of the divided areas of the photometry area close to one of the distance measuring points and other exposure compensation amounts corresponding to other divided areas.
Optionally, the compensation amount determining system determines the entire exposure compensation amount by averaging the weighted exposure compensation amounts and the other exposure compensation amounts.
Further optionally, at least one of the divided areas of the photometry area includes at least one of the plurality of distance measuring points.
Further optionally, the colorimetric system may include a blue light photometry sensor that meters blue light, a green light photometry sensor that meters green light, and a red light photometry sensor that meters red light.
Still optionally, the colorimetry system may judge at least yellow, blue and red from among yellow, magenta, cyan, blue, green and red, in accordance with the outputs of the plurality of photometry sensors, and the compensation amount determining system determines the exposure compensation amount in an over exposure side if the colorimetry system judges the color is yellow, and wherein the compensation amount determining system determines the exposure compensation amount in an under exposure side if the colorimetry system judges the color is blue or red.
In such a case, the compensation amount determining system may determine the compensation amount is zero if the colorimetry system judges the color is magenta, cyan or green.